& tex

\newcommand*{\abs}[1]{\left|#1\right|}

\title{Lorem Ipsum}
\author{John Doe}

\begin{document}

\section{First section}

This is a section.

\subsection{A subsection}

This is a subsection.

\subsubsection{A subsubsection}

This is a subsubsection.

\section{This is another subsection}

\end{document}
